CAMBRIDGE INTERNATIONAL EXAMINATIONS
GCE Advanced Level
MARK SCHEME for the October/November 2013 series
9701 CHEMISTRY
9701/41
Paper 4 (A2 Structured Questions), maximum raw mark 100
This mark scheme is published as an aid to teachers and candidates, to indicate the requirements of
the examination. It shows the basis on which Examiners were instructed to award marks. It does not
indicate the details of the discussions that took place at an Examiners’ meeting before marking began,
which would have considered the acceptability of alternative answers.
Mark schemes should be read in conjunction with the question paper and the Principal Examiner
Report for Teachers.
Cambridge will not enter into discussions about these mark schemes.
Cambridge is publishing the mark schemes for the October/November 2013 series for most IGCSE,
GCE Advanced Level and Advanced Subsidiary Level components and some Ordinary Level
components.
Page 2
1
Mark Scheme
GCE A LEVEL – October/November 2013
Syllabus
9701
Paper
41
(a)
8 e- around chlorine
1 H–electron (+) on the Cl - ion
3 covalent (ox) and one dative (oo) around N
[1]
[1]
[1]
[3]
(b) (i) it would react (with H2SO4)
[1]
(ii) CaO + H2O → Ca(OH)2
[1]
(iii) CaO absorbs more water or CaO has greater affinity for water
[1]
[3]
(c) (i) 2Ca(NO3)2 → 2CaO + 4NO2 + O2
[1]
(ii) (Down the group, the nitrates)
become more stable/stability increases
[1]
because the size/radius of ion (M2+) increases
[1]
thus causing less polarisation/distortion
of the anion/NO3-/N-O bond
[1]
[4]
[Total: 10]
© Cambridge International Examinations 2013
Page 3
2
Mark Scheme
GCE A LEVEL – October/November 2013
(a) (i) Si-Si bonds are weaker (than C-C bonds)
(ii) metallic (Sn) is weaker than (giant) covalent (Ge)
Syllabus
9701
Paper
41
[1]
[1]
[2]
(b) (i) SiCl4 + 2H2O → SiO2 + 4HCl
or SiCl4 + 4H20 → Si(OH)4 + 4HCl
or SiCl4 + 3H20 → H2SiO3 + 4HCl
(partial hydrolysis is not sufficient e.g. to SiCl3OH + HCl)
[1]
(ii) PbCl4 → PbCl2 + Cl2
[1]
(iii) SnCl2 + 2FeCl3 → SnCl4 + 2FeCl2
[1]
(iv) SnO2 + 2NaOH → Na2SnO3 + H2O
or SnO2 + 2NaOH + 2H2O → Na2Sn(OH)6
or ionic equation SnO2 + 2OH- → SnO32- + H2O
[1]
[4]
[Total: 6]
© Cambridge International Examinations 2013
Page 4
3
Mark Scheme
GCE A LEVEL – October/November 2013
Syllabus
9701
Paper
41
(a) (i) NH3 + HZ → NH4+ + ZCH3OH + HZ → CH3OH2+ + Z-
[1]
[1]
(ii) NH3 + B- → NH2- + BH
CH3OH + B- → CH3O- + BH
[1]
[1]
[4]
(b) (i) a reaction that can go in either direction
[1]
(ii) rate of forward = rate of backward reaction
or forward/back reactions occurring but concentrations of all species do not change
[1]
[2]
(c) (i) a solution that resists changes in pH
[1]
when small quantities of acid or base/alkali are added
[1]
(ii) in the equilibrium system HZ + H2O Z- + H3O+
[1]
addition of acid: reaction moves to the left
or H+ combines with Z- and forms HZ
[1]
addition of base: the reaction moves to the right
or H+ combines with OH- and more Z- formed
[1]
[5 max 4]
(d) (i) [H+] = √(0.5 × 1.34 × 10-5) = 2.59 × 10-3 (mol dm-3)
pH = 2.59/2.6 (min 1 d.p)
[1]
ecf
[1]
(ii) CH3CH2CO2H + NaOH → CH3CH2CO2Na + H2O
[1]
(iii) n(acid) in 100 cm3 = 0.5 × 100/1000 = 0.05 mol
n(acid) remaining = 0.05 – 0.03 = 0.02 mol
[acid remaining] = 0.2 (mol dm-3)
[1]
likewise, n(salt) = 0.03 mol
[salt] + 0.3 (mol dm-3)
(iv) pH = 4.87 + log(0.3/0.2) = 5.04–5.05
[1]
ecf
[1]
[6]
(e) G is CH3CH2COCl
H is SOCl2 or PCl5
J is NaCl
(or corresponding Br compounds for G, H and J; CH3CH2COBr, SOBr2, NaBr)
[2]
[Total: 18]
© Cambridge International Examinations 2013
Page 5
4
Mark Scheme
GCE A LEVEL – October/November 2013
Syllabus
9701
Paper
41
(a) (the energy change) when 1 mol of bonds
is broken in the gas phase
[1]
[1]
[2]
(b) (i) (C-X bond energy) decreases/becomes weaker (from F to I)
[1]
due to bond becoming longer/not such efficient orbital overlap
[1]
(ii) (as the bond energy of C-X decreases) the halogenalkanes become more reactive
(answer must imply that it is from F to I)
[1]
[3]
(c) The C-Cl bond is weaker than the C-F and C-H bonds
or C-Cl bond (E = 340) and C-H (E = 410)
[1]
so is (easily) broken to form Cl •/Cl radicals/Cl atoms
causing the breakdown of O3 into O2
[1]
[1]
[3]
(d) Cl-CH2CH2-CO2H
HO-CH2CH2CH2-Cl
[1]
[1]
OH
Br
[1]
[3]
(e) (i) light/UV/hν or 300°C
[1]
(ii) (free) radical substitution
[1]
(iii) ∆H = E(C-H) – E(H-Cl) = 410 – 431 = –21 kJ mol-1
[1]
(iv) ∆H = E(C-H) – E(H-I) = 410 – 299 = +111 kJ mol-1
ecf
[1]
(v) The reaction with iodine is endothermic or ∆H is positive or requires energy
[1]
(vi) Cl2 → 2Cl •
CH3CH2• + Cl2 → CH3CH2Cl + Cl •
CH3CH2• + Cl • → CH3CH2Cl
[1]
[1]
[1]
[8]
[Total: 19]
© Cambridge International Examinations 2013
Page 6
5
Mark Scheme
GCE A LEVEL – October/November 2013
Syllabus
9701
(a) (i) many monomers form a polymer
Paper
41
[1]
(ii) addition
[1]
(iii) C=C/double/π bond is broken and new C-C single bonds are formed
or double bond breaks and forms single bonds with other monomers
[1]
[3]
(b) propenoic acid
[1]
[1]
(c) (i)
carbon chain and CO2H
at least one sodium salt
(ii) 120° to 109(.5)°
due to the change from a trigonal/sp2 carbon to a tetrahedral/sp3 carbon
[1]
[1]
[1]
[1]
[4]
(d) (i)
Any four:
hydrogen bond labelled
water H-bonded to O through H atom
δ+/δ- shown on each end of a H-bond
lone pair shown on O- or C=O or H2O on a correct H-bond
Na+ shown as coordinated to a water molecule
(ii) Solution became paler and Cu(2+) swapped with Na(+)
or darker in colour and polymer absorbs water
[3]
[1]
[4]
© Cambridge International Examinations 2013
Page 7
Mark Scheme
GCE A LEVEL – October/November 2013
(e) (i) alkene(1), amide(1)
Syllabus
9701
Paper
41
[2]
(ii) NH3
[1]
(iii) H2O
[1]
(iv) HCl (aq)/H3O+ and heat/reflux (not warm)
or OH- (aq), heat and acidify
[1]
[5]
[Total: 17]
© Cambridge International Examinations 2013
Page 8
Mark Scheme
GCE A LEVEL – October/November 2013
Syllabus
9701
Paper
41
Section B
6
(a) (i) six/6 (gsv, sgv, gvs, vgs, svg,vsg)
[1]
(ii)
two displayed peptide bonds
correct formula of peptide
(iii) valine (allow glycine)
(iv) any two of:
hydrogen bonds and CO2H or OH or NH2 or CONH or CO or NH or CO2ionic bonds and NH3+ or CO2–
van der Waals’ and –CH3 or –H
[1]
[1]
[1]
2 × [1]
[6]
(b) (i) same shape/structure as substrate
(inhibitor) competes/blocks/binds/bonds to active site
or substrate cannot bind to active site
(ii) binds with enzyme and changes shape/3D structure (of enzyme/active site)
[1]
[1]
[1]
(iii)
[1]
[4]
[Total: 10]
© Cambridge International Examinations 2013
age
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GCE
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4]
[4
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Mr (of
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s)
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2 × [1]
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(
(c)
Rattio of the
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e con
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entrratiion
n off a so
olutte in e
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ch of two
o (immis
sciible
e) ssolvents
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o e
or
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buttion
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of a so
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en two
t o solv
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o P
or
PC = [X]]a/[X
X]b (a
at a consta
ant temp
perratu
ure
e)
[1]
[1]
( ) (i)
(d)
(
Kpc = [Z
Z in e
ether]]/[Z
Z in
n H2O]
O – allow
w reve
ers
se rattio
40
0 = (x
x/0.05
5)/(((4–
–x))/0.5))
= 3.2 g
(ii) Firstt ex
xtrracttion
n
0 = (x
x/0.02
25))/((4
4–x
x)//0.5
5)
40
x = 2.6
2 67 g
[1]
e f
ecf
[1]
e f
ecf
[1]
e f
ecf
[1]
(iii) Sec
cond ext
e trac
ctio
on: 1.33
3g rem
r maiin in
i ssolutio
on
Sec
cond ext
e trac
ctio
on
40
0 = (y
y/0.02
25))/((1.3
33–
–y)/0.5)
y = 0.8
0 887
7g
mas
m ss ext
e traccte
ed = 2.67
2 7 + 0.89
9 = 3..56
6/3..6 g
[4
4]
[To
ota
al: 11]
© Ca
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brid
dge
e In
nterrnattion
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xam
mina
atio
ons
s 20
013
3
Page 10
8
Mark Scheme
GCE A LEVEL – October/November 2013
Syllabus
9701
Paper
41
(a) (i) (nitrates are) soluble
[1]
(ii) Ba(2+) and Pb(2+)
[1]
SO4(2-)
[1]
BaCO3/PbCO3/CaSO4 are insoluble
[1]
[4]
(b) (i) fertilisers/animal manure
[1]
(ii) washing powder/detergents/fertilisers/animal manure
[1]
(iii) growth/production of algae/weeds/plants
or eutrophication
[1]
[3]
(c) (i) any one of:
2SO2 + O2 → 2SO3 and SO3 + H2O → H2SO4
or SO2 + NO2 → SO3 + NO and SO3 + H2O → H2SO4
or SO2 + ½O2 + H2O → H2SO4
(ii) roasting sulfide ores/extraction of metals from sulfide ores
[1]
[1]
[2]
[Total: 9]
© Cambridge International Examinations 2013